Seat belt retractors with load limiting devices are generally known and have the function to allow a load limited forward displacement of the passenger during the accident. For this purpose, seat belt retractors of this kind comprise a two-part belt shaft and a load limiting device located between the parts of the belt shaft. In that case, the safety belt restraining the passenger is fastened to one part of the belt shaft, whereas the other part of the belt shaft can be locked in relation to the vehicle-fixed housing of the seat belt retractor. When the seat belt retractor is locked and a force defined by the load limiting device is exceeded, the part of the belt shaft, to which the safety belt is fastened, can rotate in the belt extraction direction, at the same time activating the load limiting device. Thereby, the load acting upon the passenger is limited to the level defined by the load limiting device.
From DE 196 81 341 C1, for example, a seat belt retractor comprising a two-part belt shaft with a torsion bar inserted in between is known. When the belt shaft is locked and the passenger is exposed to a forward displacement, the torsion bar is plastically twisted around its own axis and thus acts as a load limiting device.
Furthermore, seat belt retractors with tensioning devices are generally known, which pull possibly present belt slack out of the safety belt system during an accident, and, thereby, couple the passenger to the vehicle deceleration preferably early.
From DE 102 13 906 A1, a seat belt retractor with a tensioning device located on the locking side of the seat belt retractor is already known. The tensioning device is coupled onto the belt shaft via the locking means of the locking device of the seat belt retractor so that the seat belt retractor has an overall small construction width. The locking of the seat belt retractor is thereby effected via a tensioner drive wheel, which can be fixed in relation to the housing frame. As the tensioner drive wheel includes both the sensor system for activating the locking device and the locking device along with the torsion bar provided as load limiting device, and as the tensioner drive wheel itself must further be designed to be lockable in relation to the housing frame, the tensioner drive wheel has a comparatively complex configuration, wherein the tensioning drive and the locking device including the connected end of the torsion bar are located next to each other.